Filament supporting structure for incandescent lamps



Aug. 19, 1947. o, CARTUN 2,425,864

FILAMENT SUPPORTINGSTRUCTURE FOR INCANDESCENT LAMPS Filed 001:. 19, 1946 n u H e m w m w e O A v I WW. 0 H D.

Patented Aug. 19, 194? UNITED STATES PATENT OFFICE FILAM'ENT SUPPORTING STRUCTURE FOR INCANDESCENT LAMPS of New York Application October 19, 1946, Serial No. 704,375

(Cl. PIG-39) ll Claims. 1

My invention relates to electric incandescent lamps and more particularly to tubular lamps of the type commonly known as show case lamps.

Tubular incandescent lamps of the type having a base at one end only and an elongated filament extending longitudinally within the bulb are commercially available at present, such lamps being commonly known as show case lamps. In their usual form, such lamps comprise a pair of lead-in conductors which project into the bulb from one end thereof and between which the filament is connected. One of these conductors is elongated and extends longitudinally of the bulb adjacent one side and to the remote end thereof where it is connected to the adjacent end of the filament. To minimize the shadow cast by the elongated conductor, it is preferable that the said conductor be as small in size as possible. For this reason, therefore, the elongated conductor-is usually made of relatively small diameter wire, of the order of 25 mil diameter or thereabouts.

In certain service applications of these show case lamps, such as in certain illuminated scales for instance, the lamp is subjected to frequent shocks and impacts. Under such conditions, the elongated lead-in wire, being more or less flexible and having its far end unsupported and therefore free to move laterally within the bulb, undergoes a considerable amount of vibration or lateral shaking movement which tends to distort the filament, causing the filament turns to short-circuit with resultant fore hortening ofthe filament life.

It is an object of the present invention therefore to provide a tubular electric incandescent lamp of the character described which will not be subject to premature filament burn-out by reason of the ordinary shocks and impacts to which the lamp may be subjected during use.

Another object of my invention is to provide a tubular electricincandescent lamp of the=character described in which the far end of the lamp mount is firmly held in place within the bulb against vibration and lateral shaking movement therein.

Still another object of my invention is to provide a filament mount for tubular electric incandescent lamps of the character described which is of simple and inexpensive construction and which will fit tightly within the bulb, irre spective of variations in the inside diameter thereof, to thereby hold the mount against vibration.

Further obj ects-and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing.

In the drawing, Fig. l is an elevation of an electric incandescent lamp comprising my invention with the envelope shown partly broken away, and Fig. 2 is an enlarged sectionon the line 2-2 of Fig. 1.

Referring tothe drawing, the lamp there shown comprises an elongated tubular glass bulb or envelope l which is evacuated and hermetically sealed. A lamp mount 2 is sealed into one end of the bulb, the said mount comprising a conventional re-entrant stemt having a pair of lead-in wires l, 5 sealed therethrough and projecting into the bulb, one of said lead-in wires ('4) being relatively short and the other "of said lead-in wires 5) being elongated. outwardly of the bulb l the lead-in wires i, 5 are electrically connected to the terminals of a conventional lamp base '6 which is suitably secured to the neck end of the bulb, as by the usual basing cement. The elongated lead-in wire 5 comprises an angular section l extending into the bulb from the stem 3, and an elongatedistraight stay section t extending longitudinally of the bulb adjacent one side of thewall thereof and having its far end curved back upon itself into a semi-circular loop 9 the free end id of which is bent inwardly towards the straight,

portion 8 of the said lead-in wire so as to extend more or less laterally of the bulb. While the elongated lead-in wire 5 may be formed as a single length of wire, the stay section 8 thereof is preferably formed as a separate piece which is spot welded or otherwise secured to the inner end of the angular section 7.

Mounted within the bulb and extending more orless longitudinally andpreferably axially thereof is an elongated coiled tungsten filament ll which is connected at its opposite ends, .under a slight tension, to the short lead-in wired and to the lateral end extension iii of the elongated lead-in wire 5. The filament ll may be secured to the lead-in wires l, 5 in any suitable Way, such as by clamping or welding. The filament l I may be disposed either inasubstantially straight line as shown, or in a Zig zag, undulating or any other desired manner. A plurality of wire supports or anchors t2 are insulatively supported on the straight section t of the elongatedlead-in wire 5, one end of each anchor wire l2 being imbedde'd'in a glass head it fusion sealed tothe straight section 8 of the lead-in wire The other end of each anchor wire it is looped around the filament, as indicated at Hi, to thereby sup port the same.

In accordance with the invention, distortion of the filament and consequent short-circuiting and early burn-out thereof under the influence of the shocks and impacts to which the lamp may be subjected during use, is prevented by the provision of suitable mean for firmly anchoring or holding the far end of the lamp mount 2 against lateral displacement and vibration within the bulb. The particular anchoring means illustrated provides a simple, convenient, and effective way of accomplishing this object. As shown, the said anchoring means comprises a spring finger I5 secured at one end to the elongated lead-in wire 5 in the region of its far end, which sprin finger is yieldable laterally of the said wire 5 and is arranged to resiliently engage the side of the bulb I opposite the side thereof adjacent the straight section 8 of the elongated lead-in wire 5, The spring finger I5 is conveniently constituted by a short length of wire of suitable springy material, 1. e., wire which will retain its springiness at the elevated temperature to which it will be subjected during the manufacture and use of the lamp. Molybdenum wire of mi] diameter or thereabouts, for example, has been found to be satisfactory for the purposes of the invention. The spring wire [5 is spot welded or otherwise secured at one end to the end loop portion 9 of the elongated lead-in wire 5 in the region of the mid-section of the loop, and it is fastened in place in a position extending backwardly from the loop and diverging slightly with respect to the straight section 8 of the lead-in wire 5. In its unfiexed position prior to insertion of the mount 2 into the bulb, the free or bulb-engaging end of the spring Wire I5 is spaced from the straight section 8 of the lead-in wire 5 a distance somewhat greater (for example at least A3" or so) than the inside diameter of the bulb I. Thus, when the mount 2 is initially introduced into the tubular bulb l for sealing thereinto, the spring wire l5 and the far end portion of the straight section 8 of lead-in wire 5 will be contracted between opposite sides of the bulb wall. The resulting deflection of the spring wire laterally inward of the tubular bulb thus serves to force the far end of the lead-in wire section 8 against the bulb wall, thereby resiliently holding the far unsupported end of the mount tightly in place within the bulb against lateral displacement and vibration therein.

As shown, the spring wire I5 is preferably bent inwardly (i. e., towards the straight section 8 of the lead-in Wire 5) at a point a short distance back from the free end thereof, as indicated at it, to provide a relatively smooth bulb-engaging surface which will not scratch the inside wall of the bulb, particularly when the latter is inside frosted, during the insertion and sealing-in of the mount 2 into the bulb.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp comprising a bulb having a tubular portion, an elongated filament within said bulb extending longitudinally of the tubular portion thereof, an elongated leadin wire projecting into the bulb substantially the full length of said filament and adjacent one side of the said tubular bulb portion, said lead-in Wire being connected at its far end to the adjacent end of the filament, and a spring finger secured at one end to the far end of said lead-in wire and yieldingly engaging the side of said tubular bulb portion opposite the side adjacent said lead-in wire to thereby resiliently hold said lead-in wire firmly against the said adjacent side of the tubular bulb portion.

2. An electric incandescent lamp comprising an elongated tubular bulb, an elongated filament extending longitudinally within said bulb, an elongated lead-in wire projecting into the bulb from one end thereof and extending longitudinally of the bulb adjacent one side and to the remote end thereof, said lead-in wire being provided at its far end with a laterally extending end portion connected to the adjacent end of the filament, and a spring finger secured at One end to the said lateral end portion of the lead-in wire and yieldingly engaging the side of the bulb opposite the side adjacent said lead-in wir to thereby resiliently hold said lead-in wire firmly against the said adjacent side of the bulb.

3. An electric incandescent lamp comprising an elongated tubular bulb, an elongated filament extending longitudinally within said bulb, an elongated lead-in Wire projecting into the bulb from one end thereof and extending longitudinally of the bulb adjacent one side and to the remote end thereof, said lead-in wire being provided with a laterally bent far end portion connected to the adjacent end of the filament, and a wire spring finger secured at one end to the said bent end portion of the lead-in wire and yieldable laterally of said lead-in wire, said spring finger engaging the side of the bulb opposite the side adjacent said lead-in wire to thereby resiliently hold said lead-in wire firmly against said adjacent side of the bulb.

4. An electric incandescent lamp comprising an elongated tubular bulb, an elongated filament extending longitudinally within said bulb, an elongated lead-in wire projecting into the bulb adja cent one side and to the remote end thereof, the far end of said lead-in wire being bent back into the shape of an open loop connected at its free end to the adjacent end of the filament, and a wire spring finger secured at one end to the said loop in the region of its mid-section and yieldingly engaging the side of the bulb opposite the side adjacent said lead-in wire to thereby resiliently hold said lead-in wire firmly against the said adjacent side of the bulb.

5. An electric incandescent lamp comprising an elongated tubular bulb, an elongated filament extending longitudinally Within said bulb, support means for said filament comprising an elongated lead in-wire projecting into the bulb from one end thereof and extending longitudinally of the bulb adjacent one side thereof and terminating at its far end in a looped extension located approximately in the plane including said lead-in wire and the longitudinal axis of the bulb and connected at its free end to the adjacent end of the filament, a wire spring finger secured at one end to the said looped extension in the region of its mid-section and located approximately in the said plane, the free end portion of said spring finger resiliently engaging the side of the bulb opposite the side adjacent said lead-in Wire to thereby hold said lead-in wire firmly against the said adjacent side of the bulb, and means supporting the filament from said lead-in wire,

6. An electric incandescent lamp comprising an elongated tubular bulb having a re-entrant stem at one end thereof, a pair of lead-in wires sealed through said stem and including a short lead-in wire and an elongated lead-in wire extending longitudinally of the bulb adjacent one side and to the remote end thereof, said elongated lead-in wire being provided at its far end with a laterally extending end portion, an elongated filament extending longitudinally within the bulb and connected between said short lead-in wire and the lateral end portion of said elongated lead-in wire, and a wire spring finger secured at one end to the said lateral end portion of the elongated lead-in wire and yieldingly engaging the side of the bulb opposite the side adjacent said elongated lead-in wire to thereby resiliently hold the latter firmly against the said adjacent side of the bulb.

'7. An electric incandescent lamp comprising an elongated tubular bulb having a re-entrant stem at one end thereof, a pair of lead-in wires sealed through said stem and including a short lead-in gated lead-in wire to thereby resiliently hold the 1 latter firmly against the said adjacent side of the bulb.

PAUL O. CART'JN. 

